In his first NFL game on Sept. 10, the former Alabama All-American suffered a high ankle sprain, and the 49ers expected he'd miss about a month. But he's already out of the orthopedic boot used to stabilize his injury.

"The one thing I know is that freak athletes tend to be freak healers as well," 49ers general manager John Lynch said.

Thursday night's game will be the second missed by Foster, who's itching to play again.

"We think the sky's the limit for Reuben," Lynch told NBC Sports Bay Area. "We just have to get him healthy, and we're going to make sure he's all the way healthy. We can't afford, with a guy like that, to put him out there too soon.

"He wanted to play the first week in the boot. That's just the way he's wired. We've got to make sure he's all the way healthy before we put him in, and we're going to do that."

The 31st player picked in the NFL Draft in April, Foster got hurt on the 11th snap on his NFL career after starting at weakside linebacker for the 49ers. During his time on the field, Foster made three tackles and broke up a pass.

San Francisco defensive coordinator Robert Saleh said there was a bright side to Foster's injury.

"He'll be in all the meetings," Saleh said. "For him to be able to sit back and absorb all the information after getting a week's worth of game time, for a rookie, believe it or not, I feel like it's almost going to be a blessing in disguise where he can just sit back. He's experienced preseason. He's experienced the game.

"And now to just watch it all from the outside, get his body back in working order where he can just kind of let things come to him rather than in the game just kind of going and going and going where he never gets to sit back and observe everything. That usually doesn't happen until their second year. For him to get this knowledge, I almost feel like it's going to be a blessing in disguise for him and the organization."

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The Rams and 49ers kick off at 7:25 p.m. CDT Thursday at Levi's Stadium in Santa Clara, California. NFL Network will televise the game.